1. Field of the Invention
The invention is directed to a multiple-clutch device, such as a double-clutch device, for arrangement thereof in a drivetrain of a motor vehicle between a drive unit and a transmission, wherein the clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission.
2. Description of the Related Art
A clutch device of this type is known, for example, from EP 0 931 951 A1. The clutch device serves to connect the drive of a motor vehicle with a multiple-speed shift transmission via two friction clutches which are preferably automatically actuated, wherein a disengagement or release system is allocated to each of these two friction clutches, so that the two friction clutches can be engaged or released independently from one another. A clutch disk of one of the two friction clutches is arranged on a central transmission input shaft so as to be fixed with respect to rotation relative to it, while a clutch disk of the other friction clutch engages at a second transmission input shaft so as to be fixed with respect to rotation relative to it, this second transmission input shaft, constructed as a hollow shaft, enclosing the central transmission input shaft. The known double-clutch is arranged with a fixed thrust plate of one friction clutch at a flywheel of an internal combustion engine. To this extent, the arrangement of the double-clutch in a drivetrain substantially corresponds to the arrangement of conventional (single-)friction clutches in the drivetrain.
Double-clutch devices (called simply double-clutches) of the type mentioned above have attracted great interest recently and are generally formed of two wet or dry clutches which are switched alternately, possibly also with overlapping. Particularly in connection with a multiple-speed shift transmission, clutches of this type make it possible to carry out shifting processes between two respective transmission speeds of the transmission without interruption of tractive forces.
In principle, double-clutch devices make it possible for both clutches to be applied jointly in especially difficult starting processes, particularly those common in car racing. For this purpose, the accelerator pedal can be deflected to its stop, as the case may be, while the motor vehicle is kept essentially stationary at the same time by applying the maximum braking force until the clutch has reached its optimal transmission point. When the braking action is canceled at the moment of reaching the optimal transmission point, the vehicle is started with maximum acceleration. Starting processes of this kind are also considered for motor vehicles with a relatively weak engine under extreme starting conditions, for example, when starting on an obstruction; that is, they are not considered only for racing cars.
Obviously, starting processes of the type described above lead to high slippage with a correspondingly extensive development of heat. This presents the problem of carrying away this heat from the area of the friction clutch serving as starting clutch. Further, a correspondingly high wear of the friction clutch must be taken into account. Moreover, heating of the friction clutches is accompanied by changes in the coefficient of friction of the friction clutches, so that control of the release mechanisms of the two friction clutches, and therefore control of the two friction clutches relative to one another, can be appreciably impaired. Since inaccuracies or changes in the functional matching of the two friction clutches relative to one another caused by heat can have the result that a torque ratio not intended in the shifting process is applied to the transmission input shafts, shifting processes in the shift transmission can be subjected to load. The synchronization in the shift transmission can be overtaxed in this way, so that, in the worst case, the shift transmission can be damaged to the point of complete failure, apart from disadvantages with respect to efficiency which occur in any case. On the whole, mismatching between the two friction clutches caused by heat is incompatible with a problem-free torque transmission in shifting processes in the shift transmission without interruption of tractive force and without jerking during shifting.
Another problem area in a double-clutch device relates to starting processes carried out in opposition to an inclination, wherein the motor vehicle must be prevented from rolling backward, or those which are used when parking at the lowest possible speed, for example, for precise positioning of a motor vehicle in a parking space. The operating states mentioned above are referred to in technical circles as xe2x80x9chill-holdingxe2x80x9d and xe2x80x9ccreepingxe2x80x9d. Both starting processes have in common that the friction clutch serving as starting clutch is operated, sometimes without actuation of the accelerator, over a longer period of time with slip. Although the torques to be transmitted in such starting processes lie well below those occurring under the operating conditions described above, especially in car racing, an intensive heating of the respective friction clutch or even both friction clutches can occur, resulting in the problems detailed above.
Suggestions have been made for gear-shifting strategies and shifting processes for double-clutch transmissions based on the aimed for adjustment of clutch slip (DE 196 31 983 C1) with consequent generation of friction heat. Depending on driving behavior, overheating problems of the type mentioned above cannot be ruled out.
The risk of intensive overheating exists not only in a dry friction clutch, but can also occur in so-called xe2x80x9cwetxe2x80x9d friction clutches, possibly in the form of a disk or plate clutch, which are operated by the action of a viscous operating medium such as hydraulic fluid. By way of example, a gear change box with two plate clutches is known from DE 198 00 490 A1, wherein one plate clutch is provided for forward driving and the other for driving in reverse. DE 198 00 490 A1 is concerned primarily with providing adequate cooling of the two plate clutches using the viscous operating medium. In spite of the liquid cooling, heating of the friction clutches is also a considerable problem in plate clutches because the operating medium, which usually flows through friction facing grooves or the like to carry off the heat, cannot be guided through between the plates in optional quantity. The reason for this is that, on one hand, excessive flow through the friction facing grooves or the like would build up a counterpressure between the friction surfaces of two adjacent plates and would therefore reduce the capacity of the friction clutches to transmit torque (with a corresponding increase in slip and therefore additional generation of friction heat, so that the problem of overheating is exacerbated) and, on the other hand, the operating medium could be overheated and destroyed when flowing through between the plates. Overheating in plate clutches can result in that the friction surfaces can no longer separate from one another completely during a disengaging process and, consequently, torques can still be transmitted via the clutch which should be disengaged, so that considerable drag torques can reach the associated shift transmission. When plate clutches are used in a multiple-clutch device, especially a double-clutch device, of the type mentioned above, shifting processes could again be brought under load in the shift transmission with resulting overtaxing of the synchronization in the shift transmission.
One approach to mastering overheating problems in the area of friction clutches in case of unfavorable operating conditions, for example, with problematic starting processes in a motor vehicle, is to provide another starting element in addition to the first and second clutch arrangements which is in the form of a hydraulic clutch or hydrodynamic clutch and comprises a hydrodynamic circuit with an impeller wheel, a turbine wheel and, if desired, a stator wheel. The driving member can be connected in parallel with one of the two friction clutches; that is, it can act on a common transmission input shaft irrespective of the engagement state of this friction clutch. A clutch device in which two plate clutches and a starting element of this type are integrated, was described in the German Patent Application 199 46 857.5 by the present Applicants which was applied for on Sep. 30, 1999 and whose disclosure is incorporated in the subject matter disclosed in the present application.
Within the framework of investigations undertaken by the present Applicants in connection with double-clutch devices, it was shown in general that wet-type clutches exhibit sealing problems and problems relating to output losses. Further, it was shown that boundary conditions relating to the available axial and radial installation space could be adhered to only with difficulty, if at all, based on the previously known concepts. With regard to clutches, such as, diaphragm clutches, which are actuated by pistons integrated in the clutch device, the arrangement of the piston chambers associated with the pistons proved especially problematic.
A multiple-clutch device, possibly a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, can be received in a clutch housing which can comprise a transmission housing cover and which is arranged or can be arranged in a stationary manner at the transmission. In this case, a housing opening is advisably closed by a lid which is arranged at the clutch housing so as to be fixed with respect to relative rotation and which has a central opening through which extends a torque transmission member, such as a clutch device hub serving as input side of the clutch device.
For an installation situation of this kind, it is suggested by way of a further development according to one aspect of the invention that a pivot bearing arrangement and/or seal arrangement is provided between an edge area of the lid defining the opening and the torque transmission member and is axially secured at the lid and/or at the torque transmission member. By means of the pivot bearing arrangement and/or sealing arrangement, the torque transmission member can be reliably guided and/or the housing interior can be reliably sealed with respect to the opening, wherein the latter is particularly important in case of a clutch device with at least one wet-type plate clutch arrangement and/or for a clutch device with an integrated hydraulic starting element. The pivot bearing arrangement and/or sealing arrangement arc/is held at the correct location even when vibrations or the like occur due to the axial securing of the pivot bearing arrangement and/or sealing arrangement at the lid part and/or at the torque transmission member.
It is suggested as a preferred further development that the lid and/or the torque transmission member has at least one retaining portion which projects radially inward or radially outward into a radial area of the pivot bearing arrangement and/or sealing arrangement and is used for axial support of the pivot bearing arrangement and/or sealing arrangement. The retaining portion on the lid side can be formed by pressed material (such as material caulking), a flange portion of the lid that is slit if desired, or a bent edge portion of the lid that is slit if desired. This applies in a corresponding manner to a retaining portion on the torque transmission member side.
The lid can be pressed into the housing opening and/or can be in a sealing engagement with the clutch housing, possibly with the intermediary of the sealing arrangement, in order to hold the lid reliably in place on the one hand and to reliably seal the housing interior on the other hand. Other steps can also be taken to secure the lid in its closed position with respect to the housing opening. Again, pressing, caulking or the like can be considered in addition to the use of a snap ring or the like.
According to another aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that the clutch device has a clutch device hub which serves as an input side of the clutch device and which has a driver arrangement, such as external teeth, for coupling a torsional vibration damper or a driven member of the drive unit and/or a driver arrangement, such as internal teeth, for coupling an operating fluid pump, e.g., an oil pump, arranged on the transmission side via a pump drive shaft. A construction which is extremely compact in its entirety and which, moreover, can easily be fitted in a drivetrain between the transmission and the drive unit can be realized by the construction of the clutch device with the clutch device hub having at least one driver arrangement for the torsional vibration damper or for the pump drive shaft. In this respect, it is extremely advantageous when the transmission input shafts are constructed as hollow shafts which are arranged one inside the other radially and enclose the pump drive shaft.
The clutch device hub can be manufactured in a particularly simple manner with respect to the driver arrangement associated with the operating fluid pump when the driver arrangement is constructed in an inner circumferential surface of the hub defining a continuous axial bore hole of the clutch device hub. Cutting tools or the like for forming the driver arrangement can then be inserted particularly easily. If necessary or if desirable, the axial bore hole can be closed in the direction of the drive unit by a separate sealing element, such as a sealing stopper, so as to be tight against operating fluid (for example, coolant).
The clutch device can have a first ring portion at which the driver arrangement associated with the torsional vibration damper or driven member is provided. It is specifically intended in this regard that the driver arrangement associated with the torsional vibration damper is formed in an outer circumferential surface of this ring portion of the clutch device hub. Further, when the clutch device hub has a second ring portion which follows the first ring portion, e.g., in the direction of the transmission and which projects radially outward over the first ring portion, it is advisable that the two ring portions are structural component parts which are produced separately and fastened to one another. The driver arrangement associated with the torsional vibration damper can then be produced in a simple manner at the first ring portion, for instance, using appropriate cutting tools, without the second ring portion hindering the application of cutting tools. The two ring portions are put together and fixed to one another, for example, by welding, to form the clutch device hub only after the driver arrangement (possibly the two driver arrangements, both of which are preferably provided at the first ring portion) is formed.
According to another aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that at least one of the clutch arrangements is a wet-type clutch arrangement, possibly a wet-type plate clutch arrangement, and that the clutch device is received in a clutch housing which possibly comprises a transmission housing cover and which is arranged or can be arranged at the transmission in a stationary manner, and a housing opening is closed by a lid which is arranged at the clutch housing so as to be fixed with respect to rotation relative to it and which has a central opening through which extends a torque transmission member, possibly a clutch device hub serving as an input side of the clutch device, wherein an edge area of the lid defining the opening is in a sealing engagement with the torque transmission member and an edge of the lid on the housing side is in a sealing engagement with the clutch housing, possibly with the intermediary of an associated sealing arrangement. A clutch device of this kind is suitable for high output losses because of the wet-type construction of the clutch arrangement and is structurally advantageous because of the construction of the housing having the lid, for example, with respect to the expenditure on production and/or assembly in the drivetrain.
The lid can project out radially relative to the housing opening and can be pressed into the housing opening.
The sealing arrangement acting between the lid and the housing can comprise at least one sealing ring, for example, an O-ring or a sealing ring having one or more lips, for a secure sealing. The sealing ring can be received in an annular groove of the lid and/or in an annular groove of the housing.
For a particularly reliable sealing it is suggested that the sealing arrangement acting between the lid and the housing comprises at least one sealing ring which is clamped axially between the housing and the lid. The sealing ring can be produced in that a sealing compound, possibly a sealing foam or an elastomer material or rubber material, is foamed on or sprayed on to the lid and/or the housing. In principle, it is also possible to produce the sealing ring by foaming or spraying an annular gap between the lid and the housing with a sealing compound, such as a sealing foam or an elastomer material or rubber material, for example, in that openings are provided in the lid for this purpose which enable a flow of material into the annular gap in the assembled state of the lid and when the lid is positioned in the housing opening.
According to another very advantageous suggestion, the sealing arrangement acting between the lid and the housing comprises a sealing compound, possibly a sealing foam or elastomer material or rubber material, which covers a transitional area between the lid and the housing so as to seal and which is applied externally, such as by spraying or foaming, with respect to an interior of the housing after the lid has been positioned in the housing opening. In addition to its function of sealing the sealing location between the lid and housing, the sealing compound also serves to secure the lid with respect to the housing, especially axially.
Another possibility consists in that the lid is secured in the housing opening by a snap ring arrangement and/or by a securing element arrangement arranged on the outside of the lid and/or housing. This holds true regardless of whether or not a sealing compound is applied externally. The securing element arrangement can comprise at least one retaining pin and/or at least one retaining bolt and/or at least one retaining screw and/or at least one retaining plate which is can, e.g., be ring-shaped.
Various phenomena which, in themselves, could impair the sealing engagement between the lid and clutch housing can occur in operation. For example, the lid can sag or become wavy with corresponding radial lift of the edge of the lid because of variations in temperature or mechanical loading, so that this edge of the lid may possibly no longer contact or be supported on the housing insofar as such contact or support of the lid is provided. Nevertheless, a sufficient sealing action can be maintained by providing a sealing arrangement which compensates for a radial lift of this kind.
Another phenomenon concerns relative movements in an axial direction between the lid or edge of the lid on the one hand and the housing on the other hand, for example, due to axial vibrations of the lid which can have different causes, i.e., on the one hand, pressure fluctuations based on the supply and removal of operating fluid, possibly, operating oil (especially a cooling fluid or cooling oil) in the interior of the housing which can excite vibrations in the lid. Further, vibrations in the lid can be excited from the radial inner side via the torque transmission member, for example, based on torsional vibrations in the drivetrain. Possible bending movements between the drive unit and the transmission can also be mentioned in this regard. In order to prevent such phenomena from impairing the sealing engagement between the lid and the housing, it is suggested that the sealing arrangement acting between the lid and the housing is suited to permit relative movements between the housing and the lid with axial movement components while retaining its sealing effect, wherein it is preferably provided that the sealing arrangement serves to damp vibrations of the lid relative to the housing, which vibrations have axial movement components. The above-mentioned sealing rings and the sealing compound applied externally to the housing are particularly suitable in this respect.
As additional securing measures or when a certain leakage can be tolerated, it is advisable when the housing has a collecting channel at least in a lower area neighboring the edge of the lid on the housing side for collecting an operating liquid, such as operating oil, supplied to the wet-type clutch device. The channel can be emptied via a drain in the course of routine maintenance steps, for example. In this case, a separate collecting reservoir communicating with the channel can be omitted. Instead of a collecting reservoir, it would also be possible for the operating liquid to return to an operating liquid circuit from the collecting channel.
The collecting channel should be offset axially in the direction of an outer side of the housing on the lid side relative to at least one sealing element of the sealing arrangement and/or a sealing location between the housing and lid in order to limit the flow of operating liquid in the channel to a minimum.
The features of a multiple-clutch and a drivetrain which were indicated in connection with the different aspects of the invention can be advantageously combined. Further independent aspects of the invention will be discerned by the person skilled in the art from the preceding explanations and the description of the Figures.
The invention is further directed to a drivetrain for a motor vehicle with a clutch device, according to at least one aspect of the invention, arranged between a drive unit and a transmission.
The invention will be described more fully in the following with reference to embodiment examples shown in the Figures.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.